1. Field of the Invention
The invention relates generally to sheet materials coated with a curable polymeric resin. More particularly, this invention relates to a curable, resin coated sheet material provided with a layer of lubricating material facilitating the use of the sheet material as a synthetic casting tape. Still more particularly, this invention relates to a curable, resin coated sheet material coated with an encapsulated lubricating material which is activated by pressure applied to the material.
2. Description of the Prior Art
Orthopedic cast materials comprising somewhat porous or woven substrates impregnated with a curable resin have been in use for quite some time. The ability of various resins to be pliable when wet and to harden when dry makes them quite suitable for use as an orthopedic cast material. The term resin is generally used herein to mean thermoplastic or water curable polymeric materials (for example, a urethane prepolymer) and the substrates may be formed from a variety of synthetic or natural fabrics such as fiberglass, polyester, cotton, etc. Some resins may be suitable which are activated by activating agents other than water. The substrates and resin may be produced in the form of discrete sheets or elongated strips wrapped into rolls and commonly referred to a synthetic cast tape.
Since any exposure to water will initiate the curing of the polymeric material normally used in synthetic cast tapes, the tapes are packaged in waterproof storage pouches in order to keep the materials dry and pliable prior to use. When the tape is ready for use, it is generally activated by being submerged in water for a short time and then wrapped around the affected limb and allowed to dry and harden into a cast as the resin cures. The resin in the tape hardens rather quickly and, while this feature makes the material quite suitable for use in cast tape, it is also a property which makes the tape tacky and difficult to work with because of the tendency of the resin material in one layer of the tape to stick to the adjacent layer of tape as it is wrapped on the limb. Once the tape is wrapped, some time is required to manipulate the tape to mold it into a cast of proper fit and the progressively increasing tackiness of the resin make it difficult for the technician to slide the various layers around relative to each other to achieve a better fit.
Not only is manipulation of the tape necessary to achieve a proper cast fit, but it is also necessary to insure strength. Because the lamination of cast tape relies on chemical rather than mechanical bonding, the tape must be wrapped firmly to minimize air pockets between the layers. The normal procedure requires the cast tape to be compressed slightly with the palms of the hands to facilitate lamination of the various layers. Since the tape is somewhat tacky at this point, the technician must use a cream or lubricating gel to prevent the tape from lifting up during the finishing process.
The aforementioned problems are solved in part by a prelubricated curable resin coated sheet disclosed in U.S. Pat. No. 4,667,661 (Scholz et al.). The resin coated sheet disclosed in this patent is coated with a lubricant which is present in an amount sufficient to reduce the kinetic coefficient of friction of the sheet material below a certain amount. The lubricant is selected from a variety of materials such as hydrophilic groups which are bonded to the curable resin or an additive, incompatible with the curable resin, such as a surfactant, a polymer comprised of a plurality of hydrophilic groups or a polysiloxane. The prelubricated sheet of the Scholz patent is a sheet which has the lubricant or surfactant coated on its surface prior to wrapping of the sheet about a substrate. While overcoming the aforementioned disadvantages, the Scholz type prelubricated sheet material tends to be slippery immediately after it is removed from the activating water bath. The slipperiness makes it difficult for the technician to hold the tape securely and manipulate it into the form of a well-fitting cast. An additional disadvantage of having the entire tape provided with a lubricious material is that the interlaminar strength of the final cast is compromised due to the interference of the lubricant with the adhesive bond between the layers.
Another prior art cast material which attempts to solve the problem of tackiness during cast formation is shown in U.S. Pat. No. 3,415,243 (Sheldon). This patent shows a cast tape wherein the cast forming reagents are encapsulated in capsules of a rupturable material placed on a substrate. Wrapping the material into a cast and either squeezing or heating the capsules ruptures them and releases the reagents which then intermix to form the hardenable cast material. This tape, however, has no slipperiness and begins to harden quickly after being wet.
It would be advantageous to provide a slippery cast tape material having the advantages of reduced interlaminar friction to facilitate proper cast formation while also having a greater degree of tackiness during the actual wrapping procedure.
It is accordingly an object of this invention to produce a water-curable, resin impregnated sheet material initially able to be firmly grasped during manual manipulation of the sheet material into a laminar cast structure and subsequently able to have some of the various layers of the laminate structure slidably moved relative to each other and relative to a user's hands.
It is another object of this invention to produce a slippery synthetic cast tape which affords the applier thereof greater control than prior art slippery tapes while also providing the requisite degree of slipperiness to facilitate cast formation.
It is a further object of this invention to produce a method and material for easily converting a conventional, non-slippery synthetic cast tape into a slippery synthetic cast tape.
It is yet another object of this invention to produce a method for converting a non-slippery cast tape to a slippery cast tape through the use of an encapsulated lubricious material adapted to be released at or near the end of the cast formation procedure.
It is also an object of this invention to produce a slippery cast tape which maintains the requisite degree of lubrication while not adversely affecting interlaminar adhesive bonds.